Cyanogen bromide splitting of human immunoglobulin M.

Human Waldenstrdm IgM (kappa) (Dau), its polypeptide chains and its F(c)5 micro and Fab micro fragments were split by cyanogen bromide (CNBr). The fragments formed by CNBr were fractionated by gel filtration, ion exchange chromatography and paper electrophoresis. They were characterized in terms of polyacrylamide disc electrophoresis, peptide maps, amino acid composition, end group determinations and limited primary structure determination. Two CNBr fragments were formed from the kappa chain, consistent with the presence of one methionine residue. Five fragments were isolated from the partially S-sulfonated micro chain. Three additional fragments were released after destruction of all disulfide bonds. The present data are unclear as to whether there are eight or nine CNBr fragments released. The comparison of CNBr pieces from the IgM, mu chain, F(c)5mu and Fab mu affords a tentative arrangement of their order, as well as the relative location of the disulfide bonds within the molecule.